Before routing wrote aboutHow to quickly build pptp VPN based on vpsArticles，But it seems there are still many people do not know exactly what that VPN，Then this article I am 818 devoted to the VPN in the end is what!
Speaking VPN，We still want to talk about the 1990s，Then this concept can not VPN，Companies to the Internet，To purchase a dedicated line (Line relate to the content we do not talk，Just know this thing called a dedicated line，And the old expensive)。Then the company opened a branch，To contact between the two companies，We must use the Internet，But not safe enough ah，You must own widening lanes to connect，Expensive maintenance costs of a force。
This time telecom operators saw an opportunity，They are on their own backbone network specifically dedicated to the deployment of a lot of green this company needs，Then leased to the company。Compared to open up its own special department to maintain a high consumption of green long terms，Leased line is too cheap，Less the cost of a sector，No maintenance costs，In addition there is someone to solve the problem，How good!
In order to facilitate the use of this time，For example, Frame Relay has also developed a technique to use to the company。At this moment，Between the branches can be used to connect a private network，It is "PN" (private network)，Since this is physically own a cable connection，Thus greatly reducing the risk of being attacked and intercepted information，And ah，Also easy to manage (such as a domain controller，Some internal resource sharing, etc., etc.)。
But there are always more cases not for leased lines，For example, a service office，Widening lanes on extravagant。This time they want to access the company's internal network，This can do it? and so，VPN technology came into being (virtual private network)，He was also called a virtual LAN，It is such a sense of。
We talked about the historical sources，So VPN is how does it work?
First, that the structure of the VPN，It is required to have a server and client can operate only，Through specific agreements，Among Internet construct a pipeline encrypted，All data sent to the server through this pipeline，Sent by the network server from where it went out，Such，Let distal clients (such as computers) seems to be also added to the local LAN among。(In this computer network perspective, it has been to that place。）
So to understand the role of VPN，你就可以理解为什么VPN可以用来科学上网了，We just need to find a server has science or natural science countries，Then sign it。Then，The angle of your computer on the Internet to "whoosh" sound to pass through that country，Jiang Zi，You can tour the Internet it!
Another use is to play the game VPN，For example, some games are country-specific server ip limited，Then through VPN technology，You can get a corresponding IP，So OK!
of course，About VPN applications certainly not limited to the "scientific" aspect，More about VPN content Liaoba we come back later!